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author | Russ Cox <rsc@golang.org> | 2024-03-27 21:46:12 -0400 |
---|---|---|
committer | Gopher Robot <gobot@golang.org> | 2024-03-28 21:25:23 +0000 |
commit | 77d9cb8937ba54a8bc82efd7f56b2bda617e4f38 (patch) | |
tree | 9859bb9423fd06d0308cf3374cfafd04ea9dafa9 | |
parent | 97f1b76b4ba3072ab50d0d248fdce56e73b45baf (diff) | |
download | go-77d9cb8937ba54a8bc82efd7f56b2bda617e4f38.tar.gz go-77d9cb8937ba54a8bc82efd7f56b2bda617e4f38.zip |
runtime: adjust when timers.adjust is called
This new logic more closely mimics what we did before my CL stack.
I had reasoned that certainly
ts.adjust(now, force=true)
ts.run(now)
would be faster than
ts.adjust(now, force=false)
ts.run(now)
ts.adjust(now, force=true)
But certainty is just an emotion, and that turns out not to be the case.
I don't really understand why the second sequence is faster,
but it definitely is, so put it back.
goos: linux
goarch: amd64
pkg: time
cpu: AMD Ryzen 9 7950X 16-Core Processor
│ s7base.txt │ s7.txt │
│ sec/op │ sec/op vs base │
AdjustTimers10000-32 263.3µ ± 4% 239.9µ ± 5% -8.87% (p=0.000 n=10)
AdjustTimers10000SingleThread-32 1.742m ± 3% 1.686m ± 8% ~ (p=0.105 n=10)
AdjustTimers10000NoReset-32 192.2µ ± 2% 194.1µ ± 1% +1.00% (p=0.009 n=10)
AdjustTimers10000NoSleep-32 237.0µ ± 2% 226.2µ ± 3% -4.55% (p=0.001 n=10)
AdjustTimers10000NoResetNoSleep-32 185.2µ ± 1% 182.9µ ± 1% -1.23% (p=0.003 n=10)
goos: darwin
goarch: arm64
pkg: time
cpu: Apple M3 Pro
│ m3base.txt │ m3.txt │
│ sec/op │ sec/op vs base │
AdjustTimers10000-12 272.6µ ± 3% 269.3µ ± 2% ~ (p=0.063 n=10)
AdjustTimers10000SingleThread-12 1.126m ± 1% 1.176m ± 1% +4.42% (p=0.000 n=10)
AdjustTimers10000NoReset-12 255.1µ ± 2% 262.6µ ± 2% +2.96% (p=0.000 n=10)
AdjustTimers10000NoSleep-12 250.2µ ± 2% 247.8µ ± 1% ~ (p=0.063 n=10)
AdjustTimers10000NoResetNoSleep-12 230.3µ ± 1% 231.0µ ± 1% ~ (p=0.280 n=10)
Change-Id: I67b5765f97dfca0142ee38e15a9904b520f51e83
Reviewed-on: https://go-review.googlesource.com/c/go/+/574740
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
-rw-r--r-- | src/runtime/time.go | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/src/runtime/time.go b/src/runtime/time.go index 42f629d168..b696c837ab 100644 --- a/src/runtime/time.go +++ b/src/runtime/time.go @@ -891,7 +891,7 @@ func (ts *timers) check(now int64) (rnow, pollUntil int64, ran bool) { ts.lock() if len(ts.heap) > 0 { - ts.adjust(now, force) + ts.adjust(now, false) for len(ts.heap) > 0 { // Note that runtimer may temporarily unlock ts. if tw := ts.run(now); tw != 0 { @@ -902,6 +902,16 @@ func (ts *timers) check(now int64) (rnow, pollUntil int64, ran bool) { } ran = true } + + // Note: Delaying the forced adjustment until after the ts.run + // (as opposed to calling ts.adjust(now, force) above) + // is significantly faster under contention, such as in + // package time's BenchmarkTimerAdjust10000, + // though we do not fully understand why. + force = ts == &getg().m.p.ptr().timers && int(ts.zombies.Load()) > int(ts.len.Load())/4 + if force { + ts.adjust(now, true) + } } ts.unlock() |